This invention relates to a process for the preparation of an olefinic product, to oxygenate conversion catalyst particles, and to a process for the manufacture of formulated oxygenate conversion particles.
Processes for the preparation of olefins from oxygenates are known in the art. Of particular interest is often the production of light olefins, in particular ethylene and/or propylene. The oxygenate feedstock can for example comprise methanol and/or dimethylether, and an interesting route includes their production from synthesis gas derived from e.g. natural gas or via coal gasification.
For example, WO2007/135052 discloses a process wherein an alcohol and/or ether containing oxygenate feedstock and an olefinic co-feed are reacted in the presence of a zeolite having one-dimensional 10-membered ring channels to prepare an olefinic reaction mixture, and wherein part of the obtained olefinic reaction mixture is recycled as olefinic co-feed. With a methanol and/or dimethylether containing feedstock, and an olefinic co-feed comprising C4 and/or C5 olefins, an olefinic product rich in light olefins can be obtained.
In the known processes a significant amount of coke-precursors such as aromatics are produced. These foul or coke the catalyst, blocking active sites and reducing catalyst activity.
U.S. Pat. No. 4,579,994 discloses the treatment of pure ZSM-5 zeolite to incorporate therein a calcium-containing compound and a phosphorous-containing compound in a
conversion reaction of methanol to olefins. This disclosure teaches to treat the zeolite as such, and mentions that the treated zeolite catalyst can be mixed with a carrier such as clay, kaolin and alumina. This is not useful method for manufacturing spray-dried catalyst particles having good attrition resistance using a silica binder. Such spray-dried particles are prepared by mixing a molecular sieve component with, inter alia, a silica binder, and requires an ion exchange after spray drying to remove the alkaline used for the preparation of the binder from the catalyst. Therefore, calcium and phosphorous previously incorporated in the zeolite may fully or partially be lost during this ion exchange.
U.S. Pat. No. 6,046,373 discloses the modification of a SAPO-34 type molecular sieve and zeolites ZSM-5 and ZSM-34, by treating with an alkaline earth metal modifying agent while applying electromagnetic energy at an effective power and frequency. Various other molecular sieves including ZSM-22 are generally mentioned, none of the examples disclose a molecular sieve having one-dimensional 10-membered ring channels. Of the examples given, Example IV, including ZSM-34 (which is an intergrowth of structure types OFF and ERI, OFF having 12- and 8-membered ring channels, and ERI having three-dimensional 8-ring channels) has poor performance in terms of methanol conversion and total C2= to C4= selectivity compared to the other examples. The example provided with the poorest performance (Example V) uses ZSM-5 having an MFI type structure as the molecular sieve.
There is a need for an improved and efficient oxygenate-to-olefins process wherein a minimum of by-products is formed.